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Benign myoepithelioma of salivary gland in palate: case report
RAFAEL SARAIVA TORRES 1 | JOEL MOTTA JUNIOR 1 | MARCELO VINICIUS DE OLIVEIRA 1 | VALBER BARBOSA MARTINS 1 | GUSTAVO CAVALCANTI DE ALBUQUERQUE 1
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ABSTRACT
Myoepithelioma are rare tumors that represent at least 1% of salivary gland tumors. The majority is benign and the parotid gland is the most common site of the tumor, followed by the palate and submandibular gland. There is no predominance between the gender and the average age is 62 years old. It appears as a mass of slow growth, generally encapsulated, painless, which leads to a delay in diagnosis. Its malignant variant, even rarer, is characterized by invasion and local destruction, metastasis is rare. The aim of this work is report a case of benign myoepithelioma on the palate, in a female patient, presenting a 15-day increase in volume in the posterior region of the palate, approximately 2.5 cm in the larger diameter, sessile, painless, consistency resilient to palpation, presenting unchanged lining mucosa, which first diagnose was pleomorphic adenoma. An excisional biopsy of the lesion was performed, presenting a trans-surgical appearance of multiple blisters. Results: Histopathological analysis reached the diagnosis of benign myoepithelioma and no recurrence was observed after 2 years of removal of the lesion. The benign myoepithelioma is a rare tumor that if treated correctly, through surgical excision, presents minimal recurrence.
Keywords: Myoepithelioma. Palate. Salivary gland neoplasms.
1 Universidade do Estado do Amazonas, Serviço de Cirurgia e Traumatologia Bucomaxilofacial (Manaus/AM, Brazil).
How to cite: Torres RS, Motta Junior J, Oliveira MV, Martins VB, Albuquerque GC. Benign myoepithelioma of salivary gland in palate: case report. J Braz Coll Oral Maxillofac Surg. 2019 SeptDec;5(3):51-5. DOI: https://doi.org/10.14436/2358-2782.5.3.051-055.oar
Submitted: March 22, 2018 - Revised and accepted: September 02, 2018
» The authors report no commercial, proprietary or financial interest in the products or companies described in this article.
» Patients displayed in this article previously approved the use of their facial and intraoral photographs.
Contact address: Rafael Saraiva Torres Rua Dom Jackson D. Rodrigues, 733, Residencial Arezzo, bl. 01, apt. 303 – Manaus/AM CEP: 69.085-833
INTRODUCTION
Myoepitheliomas was first described in 1943 1,2 . Most authors in the past considered it as an extreme variant of pleomorphic adenoma with predominant myoepithelial differentiation. 1 However, since 1991, the WHO classified the myoepithelioma as a distinct tumor, since these tumors were relatively more aggressive than pleomorphic adenoma. 2
Myoepithelioma is a rare tumor with less than 100 cases reported in the literature. 2 It is a benign salivary gland tumor and most common in the parotid, 1-5 accounting for less than 7% of salivary gland tumors. The minor salivary glands and submandibular glands may also be affected, as well as the hard and soft palate. 1
There is controversy about the classification of myoepithelioma, yet it may be divided into benign and malignant. The morphology of the tumor cell is varied with fusiform, plasmacytoid, epithelioid or clear cells. 2,3 These tumors occur in any age group from the first to the eighth decade of life, with peak incidence in the third and fourth. 1-5 Only four cases have been reported in pediatric patients below 12 years of age. 2
The benign lesion shows varied morphological growth pattern, and may be solid, myxoid or reticular with myoepithelial differentiation, differing from pleomorphic adenoma because it does not present a ductal component. 2 Clinically, it appears as a slow growing mass, generally encapsulated, circumscribed, with 1 to 5 cm in its largest diameter, usually asymptomatic and without gender predilection. 1,2,3,6
The malignant myoepithelioma is also a very rare condition, accounting for less than 2% of salivary gland carcinomas, and the most common site is the major salivary glands, particularly the parotid. However, there are reports of involvement of hard palate. 7 Most cases occur in adults, especially in women, with rare reports in children. 8 Over 50% of lesions originate from premalignant lesions: pleomorphic adenoma and benign myoepithelioma. It is characterized by local invasion and destruction, rarely presenting metastasis. 7
Total surgical removal of the lesion with a margin of unaffected normal tissue is not the first treatment choice for benign myoepitheliomas. The patients should undergo regular follow-up exams to rule out local relapse. Even though the prognosis of benign myoepitheliomas is very favorable, almost 7% of malignant transformation has been reported. 9,10
The objective of this study is to report a case of benign myoepithelioma treated by surgical excision with two-year postoperative follow-up, without evidence of relapse, to advise health professionals regarding the responsibility for the diagnosis.
CASE REPORT
A female patient aged 31 years old, of African descent, attended the Oral and Maxillofacial Surgery and Traumatology service complaining of a mass located on the palate, with evolution of 15 days, without pain complaints. The patient reported no systemic disorders or allergies. Upon physical examination, a nodular lesion was observed, resilient to palpation, presenting mucosal lining without alteration, with approximately 2.5 cm in its largest diameter, precisely in the division between hard and soft palate (Fig 1A). A CT scan was requested, which did not reveal any change in bone structures adjacent to the lesion (Fig 1B).
According to clinical data of the lesion, the previous suspected diagnosis was pleomorphic adenoma. Surgical removal was performed in an outpatient setting under local anesthesia. Intra- and extraoral antisepsis was performed local anesthesia was applied with 4% articaine with epinephrine 1:100,000. A linear incision was performed on the palatal mucosa of the lesion with a number 15 scalpel, followed by dissection and dilatation until complete removal of the lesion, not involving the overlying mucosa. During the dilatation, the coated capsule was ruptured, and the macroscopic aspect was similar to multiple glands. A safety margin of approximately 5 mm around the lesion was removed. After removal, suture was performed with resorbable Catgut (Fig 2).
Histological analysis showed multiple fragments of unmodeled dense connective tissue, showing clusters of oval cells with eosinophilic cytoplasm in plasmacytoid morphologic configuration, interpreted as neoplastic cells of myoepithelial origin compatible with benign myoepithelioma. The patient was followed for two years postoperatively, without signs of relapse (Fig 3).
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B
Figure 1: A) Intraoral aspect, evidencing lesion in the region between the hard and soft palate. Arrows indicate the limits of the lesion. B) CT scan showing no bone destruction on the palate or adjacent structures.
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Figure 2: A) Incision on the lesion. B) Divulsion after incision of the lesion. C) Tumor removal. D) Macroscopic appearance (similar to multiple glands). E) Histopathological aspect (multiple unmodeled dense connective tissue fragments, showing clusters of oval cells with eosinophilic cytoplasm in plasmacytoid morphological configuration). F) Closure of the surgical site with Catgut suture.
Figure 3: Aspect at 24 months postoperatively.
DISCUSSION
Myoepitheliomas is a rare tumor, accounting for approximately 1.5% to 2% of all tumors of major and minor salivary glands 8 , primarily affecting the parotid gland, 1,2,3,5,6 followed by tumors in minor salivary glands, e.g. located in the palate. 2 Some studies report that this neoplasm constitutes a rare type of pleomorphic adenoma. 9,10 However, according to Simpson et al, 10 it differs from pleomorphic adenoma since it exhibits little or no duct component. There are few cases reported in the literature, approximately less than 100. It can affect a wide age range, from 9 to 85 years, with higher incidence in the third decade of life. 8 In the present case, the patient was in the fourth decade of life. 2,10 It affects males and females alike; however, studies indicate higher prevalence in males, different from the present case. 2,3
Alike the present case, these tumors present as circumscribed, well-defined and encapsulated lesions, with resilient texture, painless and slow growing. 8 Politi et al 9 state that only tumors in the parotid present capsule, in contrast to the present case, since a tumor with capsule though thin, was observed on the palate. The most common diagnosis is usually pleomorphic adenoma, as reported by Ostrosky et al 3 and Padmaja et al, 1 coinciding with the diagnostic hypothesis suggested in the case.
Silveira et al 2 stated that an aspect of interest about myoepitheliomas is the little information about their biological behavior, because of their low frequency. They are benign neoplasms whose relapse is usually associated with incomplete excision. They are rarely malignant; however, its transformation into myoepithelial carcinoma may occur in tumors with long-term evolution or cases of multiple relapses. 8 Because of this, many papers consider it to be more aggressive than pleomorphic adenomas, 1,2,6 while another study found no difference in the proliferative activity between myoepitheliomas and pleomorphic adenomas. 2
The myoepithelioma should be distinguished from other salivary gland tumors, as well as their malignant variant and other soft tissue tumors that mimic myoepithelioma. Cytologically, there are four different types of myoepithelioma: spindle, plasmacytoid, epithelioid and clear cells. The pattern found in the present case was plasmacytoid.
Surgical excision is the treatment of choice for myoepithelioma, with all the surveyed papers confirming this procedure. The relapse rate is extremely low if the entire lesion is removed. The patient in question has been followed for two years and no signs of relapse were observed. Ostrosky et al 3 also stated that, due to the malignant transformation of the remaining primary disease, or due to regions that were initially malignant and were not included in the resection, this benign tumor should be removed with at least one small safety margin wherever possible, if its location permits.
It is very important that both surgeon and pathologist should have experience with salivary gland tumors, since the lack of information may lead to the chance of misdiagnosis, followed by wrong management, thus causing damage, especially to the patient. The reviewed literature correlates the lack of experience of the pathologist and dentist, and mistakes during the surgical procedure as the major causes of wrong diagnosis of this pathology. 3,10
FINAL CONSIDERATIONS
Myoepithelioma is an extremely rare tumor and thus its diagnosis is often challenging. It is very important that professionals should be familiar with such diseases to achieve a correct diagnosis and effective treatment. The chances of relapse are minimal if the correct treatment, namely surgical excision, is successfully performed.
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